This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The ability to tag proteins with GFP and its color variants has revolutionized cell biology. In particular the CFP/YFP pair and the GFP/Cherry pair of fluorescent proteins make excellent FRET partners to measure the proximity of two proteins in vivo. We plan to develop a new method to tag proteins with the GFP variants.